Abstract
We present an analysis of the photometric variability of M dwarfs in the WFCAM Transit Survey, selected from spectral types inferred by their WTS and SDSS colours, with periods detected using a Lomb- Scargle Periodogram Analisys. We estimate population membership of these objects from their tangential velocities and photometric parralaxes. Examples of M dwarfs with variable light curve morphologuies are found. We discuss possible causes for this and make use of models of spotted stars in our interpretation of the results.
Highlights
We present an analysis of the photometric variability of M dwarfs in the Wide Field Camera (WFCAM) Transit Survey, selected from spectral types inferred by their WTS and Sloan Digital Sky Survey (SDSS) colours, with periods detected using a LombScargle Periodogram Analisys
The Wide Field Camera (WFCAM) Transit Survey (WTS) is a UK Infra-red Telescope (UKIRT) Campaign Survey comprising more than 100 nights worth of observations, compiled into light curves in the J band supplemented with single, deep ZYJHK band exposures
Using a lightcurve synthesis code we find that these stars may have a high degree of spottedness, of the order of 10 per cent surface coverage or more, in some cases 50 per cent, at least at time scales of < 20 days, and we estimated a fraction for these variable M dwarfs of at least of 1 per cent from the most complete subsamples
Summary
The Wide Field Camera (WFCAM) Transit Survey (WTS) is a UK Infra-red Telescope (UKIRT) Campaign Survey comprising more than 100 nights worth of observations, compiled into light curves in the J band supplemented with single, deep ZYJHK band exposures. The observation technique is described fully by Cappetta et al [6], and the data reduction and light curve production was carried out by the Cambridge Astronomical Survey Unit (CASU) using a customised pipeline [6, 10]. These light curves permitting sensitivity to variability periods of up to tens of days. For solar-type stars the − dynamo generated at the tachocline, the boundary between the convection and radiative zones [5]. Stars later than M3.5 are fully convective, so no tachocline exists at which such a dynamo can be generated, yet stars of a later spectral type are still active and this activity may be dependent on an alternative form of dynamo [4, 15]
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